JP5856793B2 - Aluminum titanate honeycomb structure - Google Patents

Description

  The present invention relates to an aluminum titanate honeycomb structure.

  In order to purify exhaust gas discharged from an internal combustion engine such as a diesel engine, a ceramic honeycomb filter that collects particulate matter such as fine carbon particles contained in the exhaust gas by passing the exhaust gas inside is used. ing. Conventionally, a ceramic honeycomb filter has been proposed in which a honeycomb structure made of a ceramic material such as cordierite is loaded with a high specific surface area material such as activated alumina and a catalytic metal such as platinum.

  In recent years, the use of aluminum titanate has been studied as a ceramic material constituting the honeycomb structure, and its industrial utility value is increasing.

  As a method for producing aluminum titanate, a method is known in which at least an aluminum source powder and a titanium source powder are contained, and a raw material mixture containing a silicon source powder, a magnesium source powder, or the like is formed and fired as necessary (for example, , See Patent Document 1). Further, as the raw material mixture, a material containing an organic additive such as an organic binder and a pore former is used, and a green (unsintered (green)) molded body of this raw material mixture at 150 to 900 ° C. in an oxygen-containing atmosphere. A method is also known in which organic additives are removed by heating, followed by firing at 1300 ° C. or higher (paragraphs 0031 to 0032 of Patent Document 1).

WO05 / 105704 pamphlet

  By the way, there is a case where the honeycomb structure needs to be enlarged for the purpose of improving the exhaust gas purification performance of the ceramic honeycomb filter and the exhaust gas treatment efficiency. Therefore, an object of the present invention is to provide an aluminum titanate honeycomb structure that is a honeycomb structure using aluminum titanate and that can be easily increased in size.

  In order to achieve the above object, the present invention provides an adhesive layer in which a columnar aluminum titanate honeycomb fired body in which a plurality of cells are arranged in parallel in a longitudinal direction with a cell wall therebetween includes at least ceramic particles. An aluminum titanate honeycomb structure having a structure in which a plurality of bundles are bound via each other is provided.

  In the aluminum titanate honeycomb structure of the present invention, it is preferable that 30% by mass or more of the ceramic particles contained in the adhesive layer are aluminum titanate particles.

  Moreover, in the aluminum titanate honeycomb structure of the present invention, it is preferable that an average particle diameter of the ceramic particles contained in the adhesive layer is 0.2 μm or less.

  Furthermore, in the aluminum titanate honeycomb structure of the present invention, it is preferable that the adhesive layer further contains at least one of inorganic fibers and whiskers.

  According to the present invention, an aluminum titanate honeycomb structure that can be easily increased in size can be provided.

FIG. 1 (a) is a perspective view showing a preferred embodiment of the aluminum titanate honeycomb structure of the present invention, and FIG. 1 (b) is a partially enlarged view of FIG. 1 (a). is there. 1 is a perspective view schematically showing an example of a honeycomb fired body constituting an aluminum titanate honeycomb structure according to an embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  In the aluminum titanate honeycomb structure of the present embodiment, a columnar aluminum titanate honeycomb fired body in which a plurality of cells are arranged in parallel in the longitudinal direction with a cell wall interposed therebetween is provided with an adhesive layer containing at least ceramic particles. A plurality of bundled structures.

  Here, FIG. 1 (a) is a perspective view showing a preferred embodiment of the aluminum titanate honeycomb structure of the present invention, and FIG. 1 (b) is a partially enlarged view of FIG. 1 (a). is there. FIG. 2 is a perspective view schematically showing an example of the aluminum titanate honeycomb fired body constituting the aluminum titanate honeycomb structure according to the embodiment of the present invention. In the aluminum titanate honeycomb structure 10 shown in FIG. 1 (a), a plurality of square pillar-shaped honeycomb fired bodies 20 made of aluminum titanate as shown in FIG. The ceramic block 16 is configured, and the sealing material layer 12 is formed around the ceramic block 16.

  The honeycomb structure 10 of the present embodiment can be easily increased in size because a plurality of honeycomb fired bodies 20 are bundled through the adhesive layer 14. Further, the honeycomb structure 10 of the present embodiment has an effect that it is resistant to thermal shock and vibration. The reason why such an effect of being strong against thermal shock and vibration is obtained is that the temperature difference generated around each honeycomb fired body 20 even when the temperature distribution is generated in the honeycomb structure 10 due to a rapid temperature change or the like. It is presumed that this is because the difference between the maximum temperature and the minimum temperature in one honeycomb fired body 20 can be kept small, and thermal shock and vibration can be mitigated by the adhesive layer 14. Further, the adhesive layer 14 can prevent the cracks from extending to the entire honeycomb structure 10 even when cracks are generated in the honeycomb fired body 20 due to thermal stress or the like. Further, the adhesive layer 14 also serves as a frame of the honeycomb structure 10 and maintains the shape as the honeycomb structure 10. Moreover, when the adhesive layer 14 contains ceramic particles, the adhesive force between the adhesive layer 14 and the honeycomb fired body 20 is improved, and the adhesive strength between the honeycomb fired bodies 20 can be increased.

  Moreover, in the honeycomb structure 10 of the present embodiment, it is preferable that 30% by mass or more, more preferably 40% or more of the ceramic particles included in the adhesive layer 14 are aluminum titanate particles. Thereby, the adhesive force between the adhesive layer 14 and the honeycomb fired bodies 20 is improved, and the adhesive strength between the honeycomb fired bodies 20 can be further increased. Moreover, since the said effect is fully acquired, it is most preferable that all ceramic particles are aluminum titanate particles. In the present embodiment, “aluminum titanate particles” mean “aluminum magnesium titanate particles”. That is, the aluminum titanate particles may contain magnesium. The aluminum titanate particles may contain silicon. For the adhesive layer 14, particles made of alumina, silicon carbide, silica, zirconia, zeolite, mullite, cordierite, or the like can be used as ceramic particles other than aluminum titanate particles.

  In the honeycomb structure 10 of the present embodiment, the honeycomb fired body 20 is a porous body having a large number of pores, and the average pore diameter can be measured by a method described later. In the honeycomb structure 10 of the present embodiment, among the ceramic particles included in the adhesive layer 14, the number of particles having a particle diameter larger than the average pore diameter of the honeycomb fired body 20 is the ceramic particles. The total number of particles is preferably 30% or less. By setting the relationship between the average pore diameter of the honeycomb fired body 20 and the particle diameter and the number of particles of the ceramic particles contained in the adhesive layer 14 in the above range, the pores on the surface of the honeycomb fired body 20 are included. Many ceramic particles can enter and an anchor effect is generated, so that the adhesive force between the adhesive layer 14 and the honeycomb fired body 20 is increased, and the honeycomb fired body 20 is interposed through the adhesive layer 14. They can be firmly bonded together.

  Whether the relationship between the average pore diameter of the honeycomb fired body 20 and the particle diameter and the number of particles of the ceramic particles satisfies the above conditions is determined by measuring the particle size distribution of the ceramic particles and the average pore diameter of the honeycomb fired body 20. It can be judged by doing.

  The particle size distribution of the ceramic particles can be measured by a particle size distribution measuring method using a laser diffraction or scattering method. For example, a particle size distribution represented by a particle size and frequency is obtained by a laser diffraction / scattering particle size distribution measuring device, and a particle size (μm) corresponding to a frequency of 70% is counted from the smallest particle size. 70% particle diameter is calculated. Further, the average pore diameter of the honeycomb fired body 20 can be measured by a molded body pore diameter distribution measuring method by a mercury intrusion method defined in JIS R 1655.

  When the 70% particle diameter of the ceramic particles obtained by the above method is equal to or less than the average pore diameter of the honeycomb fired body 20, the ceramic particles have a particle diameter larger than the average pore diameter of the honeycomb fired body 20 The number of particles is 30% or less of the total number of the ceramic particles, and the relationship between the average pore size of the honeycomb fired body 20, the particle size of the ceramic particles, and the number of particles satisfies the above-described conditions.

In the honeycomb structure 10, the average particle diameter of the ceramic particles contained in the adhesive layer 14 is preferably 0.2 μm or less, and more preferably 0.1 μm or less. When the average particle diameter of the ceramic particles in the adhesive layer 14 is 0.2 μm or less, the bonding strength between the honeycomb fired bodies 20 can be further increased. Further, the average particle diameter of the ceramic particles is preferably 0.001 μm or more, and more preferably 0.005 μm or more, from the viewpoint of the viscosity of the adhesive. Here, an average particle diameter is a specific surface area diameter calculated | required by a BET specific surface area. The specific surface area diameter is the particle diameter of the ceramic particles assuming that the ceramic particles are all spherical, and is a value obtained by the following formula (1).
Specific surface area diameter = 6 / (ρ · BET) (1)
In the formula (1), ρ is the density of the ceramic particles. When the ceramic particles form a composite phase, the weighted average of the density of each component phase according to the mass ratio of each component phase is calculated. Density. BET means the BET specific surface area of the ceramic particles.

  In the honeycomb structure 10, the adhesive layer 14 preferably further contains inorganic fibers and / or whiskers. When these inorganic fibers and / or whiskers are included in the adhesive layer 14, the bonding strength between the honeycomb fired bodies 20 can be further improved.

  As the inorganic fiber or whisker, inorganic fiber or whisker made of alumina, silica, silicon carbide, silica-alumina, glass, potassium titanate, aluminum borate or the like is desirable. These may be used alone or in combination of two or more. Of these, aluminum borate whiskers are more desirable. In the present specification, inorganic fibers and whiskers refer to those having an average aspect ratio (length / diameter) exceeding 5. Moreover, the desirable average aspect-ratio of the said inorganic fiber and a whisker is 10-1000.

  The adhesive layer 14 is preferably formed using an adhesive paste containing an inorganic binder and / or an organic binder as a binder component in addition to the above-described ceramic particles, inorganic fibers and / or whiskers.

  As the inorganic binder, an inorganic sol, a clay binder, or the like can be used. Specific examples of the inorganic sol include alumina sol, silica sol, titania sol, and water glass. In addition, examples of the clay-based binder include double chain structure type clays such as clay, kaolin, montmorillonite, sepiolite, attapulgite, and the like. These may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of alumina sol, silica sol, titania sol, water glass, sepiolite, and attapulgite is preferable.

  Examples of the organic binder include polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and the like. These may be used alone or in combination of two or more. Of these, carboxymethylcellulose is preferred.

  The amount of the ceramic particles contained in the adhesive paste is preferably 30% by mass, and more preferably 40% by mass, based on the total solid content in the adhesive paste. On the other hand, a desirable upper limit is 80% by mass, and a more desirable upper limit is 75% by mass. If the content of the ceramic particles is less than 30% by mass, the anchor effect due to the ceramic particles entering into the pores of the surface of the honeycomb fired body cannot be sufficiently obtained, and the adhesive strength between the honeycomb fired bodies 20 tends to decrease. It is in. On the other hand, when the content of the ceramic particles exceeds 80% by mass, the adhesive strength between the honeycomb fired bodies 20 tends to decrease.

  A desirable lower limit of the total amount of the inorganic fibers and / or the whiskers contained in the adhesive paste is 5% by mass based on the total solid content in the adhesive paste. On the other hand, a desirable upper limit is 30% by mass. If the content of inorganic fibers and / or whiskers is less than 5% by mass, the strength of the adhesive layer 14 tends to decrease. On the other hand, when the content of inorganic fibers and / or whiskers exceeds 30% by mass, the bulk density of the adhesive layer 14 is lowered, and the adhesive strength between the honeycomb fired bodies 20 tends to be lowered.

  The desirable lower limit of the amount of the binder component contained in the adhesive paste (total amount of inorganic binder and organic binder) is 10% by mass based on the total amount of solids in the adhesive paste. On the other hand, a desirable upper limit is 40% by mass. When the content of the binder component is less than 10% by mass, the adhesive strength between the honeycomb fired bodies 20 tends to decrease. On the other hand, if the content of the binder component exceeds 40% by mass, the amount of ceramic particles, inorganic fibers and / or whiskers that become aggregates is insufficient, and the strength of the adhesive layer 14 tends to decrease.

  In the honeycomb structure 10, the adhesive layer 14 may not be formed over the entire side surface of the honeycomb fired body 20, and may be formed only on a part of the side surface. When the adhesive layer 14 is formed only in a part, the bulk density of the entire honeycomb structure 10 is lowered, and the temperature rise performance is improved. Moreover, since exhaust gas can contact the side surface of the honeycomb fired body 20, purification of exhaust gas can be promoted.

  Next, the honeycomb fired body constituting the honeycomb structure of the present embodiment described above will be described. The honeycomb fired body 20 shown in FIGS. 1 and 2 has a structure in which a large number of cells 22 (22a and 22b) are arranged in parallel in the longitudinal direction (in the direction of the arrow X in FIG. 2) with the cell walls 24 therebetween. Yes. The cells 22a and 22b serve as a flow path for fluid such as exhaust gas. In the honeycomb fired body 20 shown in FIGS. 1 and 2, the cells 22a and 22b are sealed at one of the openings at both ends. Has been. The cell 22a is opened and the cell 22b is sealed at the front end of FIG. 2, and the cell 22a is sealed and the cell 22b is opened at the opposite end. In the honeycomb fired body 20, such cells 22a and cells 22b are alternately arranged. The honeycomb fired body having such a structure is called a wall-flow type, and the exhaust gas passing through the honeycomb fired body is a porous cell that captures particulate matter in the exhaust gas before the exhaust. It is purified by passing through the wall 24.

  The thickness of the cell wall 24, which is the wall between the cells 22a and 22b, is not particularly limited, but a desirable lower limit is 0.05 mm, a more desirable lower limit is 0.10 mm, and a particularly desirable lower limit is 0.15 mm. On the other hand, a desirable upper limit is 0.35 mm, a more desirable upper limit is 0.30 mm, and a particularly desirable upper limit is 0.25 mm. If the thickness of the cell wall 24 is less than 0.05 mm, the strength of the honeycomb fired body 20 tends to decrease. On the other hand, when the thickness of the cell wall 24 exceeds 0.35 mm, the gas permeability tends to decrease and the exhaust gas treatment efficiency tends to decrease.

  The porosity of the cell wall 24 is preferably 30% by volume or more, more preferably 35% by volume or more, and particularly preferably 40% by volume or more. If the porosity of the cell wall 24 is less than 30% by volume, gas hardly flows through the cell wall 24, pressure loss increases, and purification efficiency tends to decrease. The porosity of the cell wall 24 is preferably 50% by volume or less, and more preferably 46% by volume or less. When the porosity of the cell wall 24 exceeds 50% by volume, soot leakage during exhaust gas purification becomes severe and the purification efficiency tends to decrease. However, since the amount of accumulated soot is reduced, the amount of heat generated during the combustion of soot is reduced, and the thermal expansion of the honeycomb fired body 20 is suppressed. The porosity of the cell wall 24 can be adjusted by the particle diameter of the raw material, the amount of pore-forming agent added, and the firing conditions. The porosity of the cell wall 24 can be measured by a mercury intrusion method.

  The average pore diameter of the cell wall 24 is preferably 10 μm or more, and more preferably 12 μm or more. Here, the “average pore diameter” of the cell wall 24 is synonymous with the “average pore diameter” of the honeycomb fired body 20 described above. If the average pore diameter of the cell wall 24 is less than 10 μm, the pores are easily blocked by the deposition of fine particles, the pressure loss increases rapidly, and the purification efficiency tends to decrease. On the other hand, the average pore diameter of the cell wall 24 is preferably 30 μm or less, more preferably 20 μm or less, and still more preferably 16 μm or less from the viewpoint of reducing fine particles that pass through the cell wall 24 without being collected. The average pore diameter of the cell wall 24 can be adjusted by the particle diameter of the raw material, the amount of pore-forming agent added, and the firing conditions. The average pore diameter of the cell wall 24 can be measured by, for example, a mercury intrusion method.

In addition, the cell density of the honeycomb fired body 20 has a desirable lower limit of 15.5 cells / cm ² (100 cpsi (cells per square inch)), and a more desirable lower limit of 46.5 cells / cm ² (300 cpsi). A more desirable lower limit is 62 / cm ² (400 cpsi). On the other hand, the desirable upper limit of the cell density is 186 cells / cm ² (1200 cpsi), the more desirable upper limit is 170.5 cells / cm ² (1100 cpsi), and the more desirable upper limit is 155 cells / cm ² (1000 cpsi). . When the cell density is less than 15.5 cells / cm ² , when the honeycomb structure 10 is used as a catalyst carrier for purifying the exhaust gas, the area of the wall in contact with the exhaust gas inside the honeycomb fired body 20 becomes small. Tend. On the other hand, when it exceeds 186 pieces / cm ² , the pressure loss increases and the honeycomb fired body 20 tends to be difficult to manufacture.

The honeycomb fired body 20 preferably has a BET specific surface area of 0.1 to 20 m ² / g. If the BET specific surface area of the honeycomb fired body 20 is less than 0.1 m ² / g, the purification efficiency tends to decrease. On the other hand, when the BET specific surface area of the honeycomb fired body 20 exceeds 20 m ² / g, uneven catalyst metal loading tends to occur when the catalyst is loaded, which will be described later. The BET specific surface area can be measured using, for example, a commercially available gas adsorption device.

  In addition, the cross-sectional shape of the cells 22a and 22b formed in the honeycomb fired body 20 is not particularly limited. For example, a triangle, a rectangle, a hexagon, an octagon, a circle, or the like other than the square as shown in FIG. It may be a combination of a plurality of shapes.

  Further, the shape of the honeycomb fired body 20 is not particularly limited, but the honeycomb fired bodies 20 are preferably in a shape in which the honeycomb fired bodies 20 are easily bundled via the adhesive layer 14, and a cross section perpendicular to the longitudinal direction thereof. Examples of the shape include triangles, rectangles, hexagons, octagons, and fan shapes in addition to the squares shown in FIG. Further, the honeycomb structure 10 may be formed by combining a plurality of honeycomb fired bodies 20 having different shapes.

  The honeycomb fired body 20 includes at least aluminum titanate. The other constituent materials are not particularly limited, but the honeycomb fired body 20 preferably further contains inorganic fibers and / or whiskers. When the honeycomb fired body 20 contains inorganic fibers and / or whiskers, the strength of the honeycomb fired body 20 can be further improved. As the inorganic fiber and / or whisker, the same kind of material as the inorganic fiber and / or whisker contained in the adhesive layer 14 described above can be used. The inorganic fibers and / or whiskers used as the raw material for the honeycomb fired body 20 and the inorganic fibers and / or whiskers used as the raw material for the adhesive layer 14 may be the same material or different materials. Good.

  In addition to the aluminum titanate, the honeycomb fired body 20 may contain particles made of alumina, silica, zirconia, titania, ceria, mullite, zeolite, or the like as inorganic particles. These particles may be used alone or in combination of two or more. Of these, alumina particles and ceria particles are preferable.

  In the present embodiment, the aluminum titanate in the honeycomb fired body 20 may contain magnesium or silicon. Although the aluminum content rate in the aluminum titanate in the honeycomb fired body 20 is not particularly limited, for example, it is 40 to 60 mol% in terms of aluminum oxide. Although the content rate of titanium in aluminum titanate is not specifically limited, For example, it is 35-55 mol% in conversion of titanium oxide. The magnesium content in the aluminum titanate is preferably 1 to 5% by mass in terms of magnesium oxide. In addition, what is necessary is just to adjust suitably the composition of aluminum titanate with the composition of a raw material mixture. In addition to the above components, the aluminum titanate may contain a component derived from the raw material or a trace component inevitably mixed in the work-in-process in the production process.

  Regarding the total amount of the inorganic fibers and / or the whiskers contained in the honeycomb fired body 20, a desirable lower limit is 3% by mass, a more desirable lower limit is 5% by mass, and a further desirable lower limit is 8% by mass. On the other hand, a desirable upper limit is 70% by mass, a more desirable upper limit is 50% by mass, a further desirable upper limit is 40% by mass, and a particularly desirable upper limit is 30% by mass. If the content of inorganic fibers and / or whiskers is less than 3% by mass, the strength of the honeycomb structure 10 tends to decrease. On the other hand, when the content of inorganic fibers and / or whiskers exceeds 70% by mass, there is a tendency to cause mold clogging when a raw material mixture, which will be described later, is molded.

  When the wall-flow type honeycomb fired body 20 shown in FIG. 2 is manufactured, the cells of the formed body are sealed at any timing after forming the formed body, after drying, or after firing. Sealing is performed by filling a plugging material into the opening at one end of the cell. As the constituent material of the sealing material, the same material as that of the honeycomb fired body 20 is usually used.

  1 and 2 show a wall-flow type honeycomb fired body, the honeycomb fired body is a flow-through type in which neither of the openings at both ends of the cell 22 is sealed. It may have the following structure.

  The honeycomb structure 10 desirably carries a catalyst. The catalyst is not particularly limited, and examples thereof include noble metals, alkali metals, alkaline earth metals, and oxides. These may be used alone or in combination of two or more.

Examples of the noble metal include platinum, palladium, rhodium, ruthenium, nickel, and alloys thereof, and at least one of platinum or palladium is preferable. Examples of the alkali metal include potassium and sodium. Examples of the alkaline earth metal include barium. Examples of the oxide include perovskite (La _0.75 K _0.25 MnO _{3 and the} like), CeO _{2 and the} like. Further, the honeycomb structure 10 may carry a promoter such as ceria or zirconia.

  The timing for loading the catalyst is not particularly limited, and the catalyst may be loaded after the honeycomb structure 10 is manufactured, or may be loaded at the raw material stage of the honeycomb fired body 20. Moreover, the catalyst loading method is not particularly limited, and for example, it can be carried out by an impregnation method or the like.

  The use of the honeycomb structure (ceramic honeycomb filter) 10 as described above is not particularly limited. For example, the honeycomb structure (ceramic honeycomb filter) 10 is suitable for an exhaust gas filter used for exhaust gas purification of an internal combustion engine such as a diesel engine or a gasoline engine. Can be applied.

  Next, a method for manufacturing the honeycomb structure of the present embodiment will be described.

  First, an aluminum source, a titanium source, and an inorganic compound containing a magnesium source and a silicon source added as necessary, the inorganic fiber and / or whisker, a binder component, and the like, which are raw materials for the aluminum titanate, are mixed. A raw material mixture is obtained. In addition to the above, a pore former, a lubricant, a plasticizer, a dispersant, a solvent, and the like can be added to the raw material mixture as necessary.

  Here, the inorganic compound is a raw material of aluminum titanate. When a magnesium source is added to the inorganic compound, an aluminum magnesium titanate crystal is formed by firing to obtain a honeycomb fired body with further improved heat resistance. be able to. In addition, it replaces with a part or all of the said inorganic compound which is a raw material of aluminum titanate, You may use the aluminum titanate and aluminum magnesium titanate crystallized previously.

  Further, as the binder component, the same material as the binder component contained in the adhesive layer 14 described above can be used. Note that the binder component used as the raw material of the honeycomb fired body 20 and the binder component used as the raw material of the adhesive layer 14 may be the same material or different materials.

  The amount of the binder component contained in the raw material mixture is preferably 5% by mass, more preferably 10% by mass, and more preferably 15% by mass based on the total solid content of the raw material mixture. is there. On the other hand, a desirable upper limit is 50 mass%, a more desirable upper limit is 40 mass%, and a more desirable upper limit is 35 mass%. When the amount of the binder component is within the above range, there is a tendency that stable molding can be performed when a raw material mixture described later is molded.

  Examples of the pore-forming agent include carbon materials such as graphite; resins such as polyethylene, polypropylene, and polymethyl methacrylate; plant materials such as starch, nut shells, walnut shells, and corn; ice; and dry ice.

  Examples of the lubricant and plasticizer include alcohols such as glycerin; higher fatty acids such as caprylic acid, lauric acid, palmitic acid, alginic acid, oleic acid and stearic acid; metal stearates such as Al stearate; polyoxy An alkylene alkyl ether is mentioned.

  Examples of the dispersant include inorganic acids such as nitric acid, hydrochloric acid and sulfuric acid; organic acids such as oxalic acid, citric acid, acetic acid, malic acid and lactic acid; water; alcohols such as methanol, ethanol and propanol; ammonium polycarboxylate And the like.

  Examples of the solvent include water; alcohols such as methanol, ethanol, butanol, and propanol; glycols such as propylene glycol, polypropylene glycol, and ethylene glycol.

  The preparation of the raw material mixture is not particularly limited, but is preferably performed by mixing and / or kneading the above-described materials. Mixing can be performed using a mixer, an attritor, etc., for example. The kneading can be performed using, for example, a kneader.

  Next, by molding the raw material mixture obtained above, a honeycomb-shaped molded body (green molded body) is obtained. A method for molding the raw material mixture is not particularly limited, but it is preferable to mold the raw material mixture into a shape having cells.

  Next, the obtained molded body is subjected to a drying treatment using a dryer as necessary. Examples of the dryer include a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, and a freeze dryer.

  After molding or drying, the molded body may be sealed. Sealing is performed, for example, by filling the opening at one end of the cells 22a and 22b with a sealing material as shown in FIG. In this case, the sealing material is, for example, a sealing material provided only at the end of the cell 22a by bringing a mask provided with a plurality of through holes in a desired position into close contact with one end surface of the molded body and supplying the sealing material thereto. The other end surface of the molded body can be filled in the same manner by filling only the end portion of 22b with the sealing material. As a result, as shown in FIG. 2, a molded body is obtained in which the cells 22a whose one end opening is sealed and the cells 22b whose opposite opening to the cell 22a are alternately arranged are arranged. Can do.

  As the sealing material, the same material as that of the molded body can be usually used. Further, as the sealing material, a material different from that of the molded body can be used.

  In addition, you may perform sealing after the below-mentioned baking. In that case, baking is performed again after sealing. In the case where sealing is performed on the molded body before firing, the firing process is only required once, which is preferable.

  Next, the honeycomb formed body that has been subjected to a drying treatment as necessary is calcined (degreasing) and fired. The calcination (degreasing) is a process for removing the organic binder in the honeycomb formed body and the organic additive blended as necessary by burning, decomposition, or the like, and typically reaches the firing temperature. Up to a temperature rising stage (for example, a temperature range of 150 to 900 ° C.). In the calcination (degreasing) step, it is preferable to suppress the temperature increase rate as much as possible.

  Firing can be performed, for example, by placing the green molded body in a firing furnace and heating. The firing temperature is usually 1300 ° C. or higher, preferably 1400 ° C. or higher. On the other hand, from the viewpoint of making the obtained honeycomb fired body easy to process, the firing temperature is usually 1650 ° C. or lower, preferably 1600 ° C. or lower, more preferably 1550 ° C. or lower. The rate of temperature increase up to the firing temperature is not particularly limited, but is usually 1 ° C./hour to 500 ° C./hour. When the honeycomb formed body includes the silicon source powder, it is preferable to provide a step of holding at a temperature range of 1100 to 1300 ° C. for 3 hours or more before the firing step. Thereby, melting and diffusion of the silicon source powder can be promoted.

  Firing is usually performed in the air, but depending on the components and component ratio of the raw material mixture, firing may be performed in an inert gas such as nitrogen gas or argon gas, or carbon monoxide gas, hydrogen gas, etc. You may bake in such reducing gas. Further, the firing may be performed by lowering the water vapor partial pressure in the firing atmosphere.

  Firing is usually performed using a conventional firing furnace such as a tubular electric furnace, a box-type electric furnace, a tunnel furnace, a far-infrared furnace, a microwave heating furnace, a shaft furnace, a reflection furnace, a rotary furnace, or a roller hearth furnace. Done. Firing may be performed by a batch type or a continuous type. Moreover, baking may be performed by a stationary type or may be performed by a fluid type.

  The firing time varies depending on the type of firing furnace, firing temperature, firing atmosphere, and the like, but is usually from 10 minutes to 300 hours.

  As described above, it is possible to obtain a columnar honeycomb fired body in which a large number of cells are arranged in parallel in the longitudinal direction with a cell wall therebetween. The obtained honeycomb fired body has a shape that substantially maintains the shape of the honeycomb formed body immediately after forming. The obtained honeycomb fired body can be processed into a desired shape by grinding or the like.

  Next, an adhesive paste that is a raw material of the adhesive layer 14 is prepared. The adhesive paste is a paste containing at least ceramic particles, which is a raw material for the adhesive layer of the honeycomb structure as described above. Preferably, 30% by mass or more of the ceramic particles are aluminum titanate particles. There is something. Further, among the ceramic particles contained in the adhesive paste, the number of particles whose particle diameter is larger than the average pore diameter of the honeycomb fired body to be bonded is 30% or less of the total number of ceramic particles. It is preferable that

  In addition, the particle size distribution of the ceramic particles contained in the adhesive layer 14 after the honeycomb structure 10 is obtained through the steps described later is equivalent to the particle size distribution of the ceramic particles contained in the raw material of the adhesive layer 14. is there. Therefore, the honeycomb structure 10 to be manufactured is bonded by controlling the relationship between the particle diameter and the number of particles of the ceramic particles to be blended when preparing the adhesive paste and the average pore diameter of the honeycomb fired body 20 within the above range. The relationship between the particle diameter and the number of the ceramic particles contained in the agent layer 14 and the average pore diameter of the honeycomb fired body 20 can be controlled within the above range. The particle size distribution of the ceramic particles can be adjusted by a conventionally known method such as classification.

  In addition, since it mentioned above about the detail of the material contained in the said adhesive paste, and the compounding quantity of each material, the description is abbreviate | omitted.

  Next, the plurality of honeycomb fired bodies 20 are bundled to form a honeycomb aggregate having a predetermined size. The formation of the honeycomb aggregate is, for example, a method in which an adhesive paste layer is formed by applying an adhesive paste to the side surface of each honeycomb fired body 20 and the honeycomb fired bodies 20 are sequentially bound, or the ceramic block 16 to be manufactured is formed. Each honeycomb fired body 20 can be temporarily fixed in a form having substantially the same shape as the shape, and an adhesive paste can be injected between the honeycomb fired bodies 20. The honeycomb aggregate is heated to dry and solidify the adhesive paste layer, thereby forming the ceramic block 16 in which the honeycomb fired bodies 20 are firmly bonded to each other via the adhesive layer 14.

  Note that the number of the honeycomb fired bodies 20 to be bundled may be appropriately determined according to the size of the target honeycomb structure 10. Further, the ceramic block 16 may be cut, polished, or the like as necessary to have a cylindrical shape as shown in FIG.

  Moreover, it is preferable that the thickness of the adhesive bond layer 14 formed by the said process is 0.5-5 mm. If the thickness of the adhesive layer 14 is less than 0.5 mm, sufficient bonding strength may not be obtained. On the other hand, since the adhesive layer 14 is a part that does not function as a catalyst carrier or a filter, when the thickness exceeds 5 mm, the specific surface area per unit volume of the honeycomb structure 10 is reduced, and the exhaust gas purification performance and the exhaust gas treatment efficiency are improved. There is a tendency to decrease. Moreover, when the thickness of the adhesive layer 14 exceeds 5 mm, the pressure loss may increase.

  Next, if necessary, the sealing material layer 12 is formed by applying a sealing material paste to the outer peripheral surface of the ceramic block 16, drying and fixing the ceramic material. By forming the sealing material layer 12, the outer peripheral surface of the ceramic block 16 can be protected, and as a result, the strength of the honeycomb structure 10 can be increased.

  The raw material of the sealing material paste is not particularly limited, and may be made of the same raw material as the adhesive paste, or may be made of a different raw material. Moreover, when the said sealing material paste consists of the same raw material as the said adhesive paste, the compounding ratio of the structural component may be the same as the said adhesive paste, and may differ.

  Although the thickness of the said sealing material layer 12 is not specifically limited, It is desirable that it is 0.1-2 mm. If the thickness is less than 0.1 mm, the outer peripheral surface may not be protected and the strength may not be increased. If the thickness exceeds 2 mm, the specific surface area per unit volume of the honeycomb structure 10 is reduced, and exhaust gas purification performance and exhaust gas are reduced. Processing efficiency tends to decrease.

  Further, in this manufacturing method, after the plurality of honeycomb fired bodies 20 are bundled through the adhesive layer 14 (in the case where the sealing material layer 12 is provided, after the sealing material layer 12 is formed) It is desirable to bake. Thereby, when the organic binder is contained in the adhesive bond layer 14 and the sealing material layer 12, degreasing and removal can be performed. The conditions for calcining are appropriately determined according to the type and amount of organic matter contained, but it is preferably about 700 ° C. for about 2 hours.

  By such a method for manufacturing a honeycomb structure, a large-sized aluminum titanate honeycomb structure can be easily manufactured.

[Example 1]
(Preparation of adhesive)
90% by mass of alumina sol-100 (trade name, manufactured by Nissan Chemical Industries, Al ₂ O ₃ : 10%), and a powder having a composite phase of aluminum magnesium titanate and aluminosilicate glass (Al _1.82 Mg _0.12 Ti _1.12 O _6.09 -0.1SiO ₂₎ was mixed with 10 mass%, to prepare an adhesive. The solid content mass ratio in this adhesive was Al ₂ O ₃ : Aluminum magnesium titanate ceramic powder (Al _1.82 Mg _0.12 Ti _1.12 O _6.09 −0.1 SiO ₂ ) = 47: 53 Met. It was 180 m < ² > / g when the BET specific surface area of the ceramic particle obtained by drying this adhesive agent at 200 degreeC for 2 hours was measured. _Also, the true density of Al 2 TiO ₆ is 3.7 g / cm ^3, since the true density of the boehmite is 3.05 g / cm ^3, the average value of the density of the ceramic particles in the adhesive 3.36g / Cm ³ . Using the average value of the BET specific surface area and density, the specific surface area diameter of the ceramic particles was 10 nm as calculated by the above formula (1). _{Incidentally,} using the value of the density of _Al 2 TiO ₆ as the density of the _{Al 1.82 Mg 0.12 Ti 1.12 O 6.09} -0.1SiO 2.

(Production of ceramic honeycomb fired body)
In order to form a green honeycomb molded body, raw material powder of aluminum magnesium titanate (Al ₂ O ₃ , TiO ₂ , MgO), ceramic powder having a composite phase of SiO ₂ , aluminum magnesium titanate, alumina, and aluminosilicate glass (Composition formula at the time of preparation: 41.4 Al ₂ O ₃ -49.9 TiO ₂ -5.4 MgO-3.3SiO ₂ , the numerical values in the formula represent a molar ratio), an organic binder, a lubricant, a pore former, A raw material mixture containing a plasticizer, a dispersant and water (solvent) was prepared. The content of each component in the raw material mixture was adjusted to the following values.
Al ₂ O _3: 37.3 parts by weight.
TiO ₂ : 37.0 parts by mass.
MgO: 1.9 parts by mass.
SiO ₂ : 3.0 parts by mass.
Ceramic powder: 8.8 parts by mass.
Pore-forming agent: 12.0 parts by mass of starch having an average particle size of 25 μm obtained from potato.
Organic binder: 7.8 parts by mass.
Plasticizer: 0.4 parts by mass.
Dispersant: 4.6 parts by mass.
Water: 28.3 parts by mass.

  The above raw material mixture is kneaded and extruded to form a honeycomb-shaped green (unfired) molded body having a plurality of open cells at both ends partitioned by partition walls (1 in a cross section perpendicular to the direction of extrusion). A prismatic body having a side of 50 mm was produced. The green honeycomb molded body was cut to a length of 250 mm and dried by microwaves under normal pressure. After sealing the both ends in the longitudinal direction of the dried body so that the dried green honeycomb molded body becomes the wall flow type shown in FIG. 2, the oxygen concentration of the atmosphere is set to 3% by volume or less, and the heating rate is 10 ° C./hour. The temperature was raised to 600 ° C. and then fired at 1450 ° C. for 5 hours to obtain an aluminum titanate fired body (honeycomb fired body). The cross-sectional shape of the obtained honeycomb fired body (the prism body after firing) was a square having a side of 42 mm. The partition wall thickness was 0.28 mm.

  The four fired honeycomb fired bodies thus obtained were assembled on a block and bonded together with an adhesive, and then heated at 500 ° C. for 1 hour to cure the adhesive, thereby making a ceramic (aluminum titanate) honeycomb structure having a side of 85 mm. Obtained.

  As described above, according to the present invention, it is possible to provide an aluminum titanate honeycomb structure that can be easily increased in size.

DESCRIPTION OF SYMBOLS 10 ... Honeycomb structure, 14 ... Adhesive layer, 20 ... Honeycomb fired body, 22a, 22b ... Cell, 24 ... Cell wall.

Claims (2)

A columnar aluminum titanate honeycomb fired body in which a plurality of cells are arranged in parallel in the longitudinal direction across a cell wall has a structure in which a plurality of cells are bound only through an adhesive layer containing at least ceramic particles, An aluminum titanate honeycomb in which the ceramic particles contained in the adhesive layer have an average particle size of 0.2 μm or less, and 30% by mass or more of the ceramic particles contained in the adhesive layer are aluminum magnesium titanate particles. Structure. Wherein the adhesive layer inorganic fibers and whisker is further included, aluminum titanate honeycomb structure according to claim 1.

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